The s of Testing CNG Retail Motor Fuel Dispensers 1
Certain commercial entities, equipment, or materials may be identified in this presentation in order to describe a procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for that purpose. Disclaimer 2
Photo courtesy of Kulp Energy Solutions
Provide an overview of the inspection of CNG retail dispensing equipment Will teach some of what you need to know Not intended to fully prepare you for an official field inspection Familiarize you with many of the more important operational features of a typical retail CNG dispenser Identify the equipment you will need to perform an official test Familiarize you with important safety considerations relating to CNG and the equipment used to dispense it in a retail application. Follow up with in-field training. Presentation Objectives 4
Slow Fill (Time Fill) Where a vehicle sits for hours to be refueled by small compressors. Vehicle Refueling Appliance (VRA) Intended for home refueling. Fast Fill: Where natural gas is typically received from the gas company, run through a compressor to storage cylinders, then dispensed into a vehicle from a retail motor fuel dispenser (Refuel time is 5 to 7 minutes). Refueling Stations 5
Photo courtesy of Tulsa Gas Technologies, Inc. CNG Fast-Fill Station 6
Photo courtesy of Tulsa Gas Technologies, Inc.
8 Photo Courtesy of Tulsa Gas Technologies, Inc.
Photo courtesy of Tulsa Gas Technologies, Inc.
CNG Fuel System (A) Natural gas fill valve (B) High-pressure cylinders (C) Master manual shut-off valve (D) High-pressure fuel line (E) Regulator to reduce pressure to fuel injection pressure (F) Solenoid valve (G) Carburetor or fuel-injection system 10 Photo courtesy of U.S. Dept. of Energy
Photos courtesy of Altenesol, LLC Steps to Refueling 13
Photos courtesy of Altenesol, LLC Steps to Refueling 14
Photo Courtesy of Tulsa Gas Technologies, Inc.
Photo Courtesy of Tulsa Gas Technologies, Inc.
Photo courtesy of reason Metrology Consulting, LLC
A compressor receives gas from the pipe line Compresses the gas using multi-stage cylinders into storage vessels or to a vehicle The dispenser meters and controls the gas from storage or the compressor to the vehicle in Gasoline Gallon Equivalent units How Natural Gas is Compressed 19
Illustration courtesy of Tulsa Gas Technologies, Inc.
21 Photo courtesy of CA. Div. of Measurement Standards
Photo courtesy of Tulsa Gas Technologies, Inc.
Photo courtesy of Tulsa Gas Technologies, Inc. Where Natural Gas is Stored Once Compressed 25
Service Pressure: the settled pressure at a gas temperature of 70 o F and full gas content marking of a vehicle fuel tank is normally located behind the fuel access cover beside the fill tube Maximum Working Pressure: a required safety marking on the dispenser to indicate its designed maximum operating pressure Pressure Terms 28
When the temperature of the CNG being dispensed is 70 o F, fuel tank will be full and dispenser will shut off at the rated service pressure of the fuel tank If greater than 70 o F, the dispenser will continue filling a fuel tank beyond its rated service pressure to compensate for the increased temperature of the gas If less than 70 o F, the dispenser will stop the flow of gas before reaching the rated service pressure of the fuel tank Filling a Tank: The Effect of Temperature 29
CNG Dispenser Gasoline Dispenser Design Similarities
31 Photo courtesy of CA. Div. of Measurement Standards
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Highly flammable can be ignited by heat, flames, sparks or other sources of ignition (e.g., static electricity, etc.) Set up scale outside of classified area (beyond 5 feet from hose connection to dispenser) Ground the test tank when transferring product Product is under high pressure (3600 psi) Skin may freeze if exposed to product and result in frostbite CNG is normally treated with an odorant smell for leaks Pay particular attention to the test tank under high pressure When released, CNG displaces oxygen considered an asphyxiant - lighter than air Inflammability Inspection Safety 37
The H-44 Codes that Apply: 1.10 General Code 3.37 Mass Flow Meters The NIST EPO that Applies: No. 28 Compressed Natural Gas Retail Motor Fuel Dispensers (Updated 2012) Code Application
Many design and user requirements applicable to a gas pump are the same or similar to those that apply to a CNG dispenser: Zero-set back interlock Diversion of product Display of quantity, unit price, and total sale for devices that compute Values defined Hose length Steps after dispensing, etc. Code Similarities 39
Delivered quantity must be indicated in Gasoline Gallon or Gasoline Liter Equivalent (GGE or GLE) d for GGE 0.001 GGE (d for GLE 0.01 GLE) Dispenser must provide an indication of the mass for each transaction either: continuously, on an internal or external display; or by using controls on the device. Value of d for mass 0.001 lb. or 0.001 kg. Significant Differences 40
Discharge hose must automatically pressurize before registering any delivery of product Some marking requirements differ: Minimum measured quantity Max and min flow rates in pounds per unit of time ratio of max to min 10:1 Maximum working pressure Meter accuracy class Significant Differences 41
Photo courtesy of CA. Div. of Measurement Standards
Suitable Scale: Intrinsically safe: must meet Underwriters Laboratory (UL) acceptability for use in weighing Class I, Division 2 product Of sufficient capacity to weigh a full test cylinder Appropriate division size to minimize rounding errors Class F field standard test weights Suitable Test Cylinder: Rated equal or greater than the service pressure marked on the device Compatible fittings, bleed valve, pressure gauge, etc. Equipment Required for Testing 43
Tank Used for Gravimetric CNG Meter Test Type 3 Tank Steel Wrapped in Fiberglass Photo courtesy of reason Metrology Consulting, LLC
Test Tank Label 45
300 lb capacity with a 0.05 lb resolution (d) Reference Scale Photos courtesy of reason Metrology Consulting, LLC 46
Photo courtesy of reason Metrology Consulting, LLC Verifying Accuracy of Scale 50 lb class F weights
Verify the appropriateness of the reference scale Verify that the maximum working pressure of the test cylinder will not be exceeded during tests Conduct test for computer jump with test tank empty (i.e., less than 200 psi) Conduct test drafts at 1/3 rd, 2/3 rd, and full capacity of the test cylinder and at maximum flow rate Empty the test cylinder return product to owner/operator Test Overview 48
Repeat the previous tests If the minimum measured quantity (MMQ) is less than the smallest test draft, conduct a test draft at the MMQ value Check effectiveness of zero-set-back interlock Check for proper operation of the low-flow cut-off valve Power loss test device memory to retain quantity and price during power loss Test Overview 51
After each test draft, verify correct conversion of mass to gasoline gallon equivalent (GGE) Indicated value of GGE x 5.660 must equal value of the mass to the closest 0.001 lb. Check price computation Quantity delivered (in GGE) x unit price must equal total sale to the nearest cent Print a ticket after each test draft Verify all values printed on receipt agree with values indicated on dispenser Additional Checks 52
Provided an overview of the inspection of CNG retail dispensing equipment Provided instruction on a lot of what you need to know Hopefully you can build on this instruction to better prepare you for conducting actual field inspections Provided pictures and explained many of the more important operational features of a typical retail CNG dispenser Provided pictures and explained the equipment needed to enable you to perform an official test Familiarize you with important safety considerations relating to CNG an the equipment used to dispense it in a retail application. Summary 53
Central Weights and Measures Association: For allowing NIST OWM the opportunity to provide this short technical presentation to their membership during the 2012 CWMA Annual Conference. Photographs and illustrations courtesy of: Tulsa Gas Technologies Kulp Energy Solutions U.S Department of Energy reason Metrology Consulting, LLC CA Division of Measurement Standards NIST OWM Special Thanks 54
Thank YOU Direct Questions to: Rick Harshman (richard.harshman@nist.gov) Office of Weights and Measures 301-975-8107 55